The use of lasers in medical procedures has increased significantly in the last few years. Medical laser devices include a laser engine for generating a high power treatment beam. A means is provided for delivering the treatment beam to the treatment site. The type of delivery means is dependent upon the wavelength of the laser radiation. For example, optical fibers have been developed to carry wavelengths in the visible and near infrared regions of the spectrum.
In most fiber delivery systems, the laser output exits the fiber substantially along its longitudinal axis. Fiber delivery systems have also been developed wherein the output beam is redirected so that it exits the probe at an angle relative to the axis of the fiber. By redirecting the angle of the beam, treatment sites can be reached which are not in line with the fiber. In addition, the probe can be used in a manner more similar to a mechanical knife.
One approach for redirecting the beam is to place a mirrored surface or a prism beyond the end of the fiber. Examples of such approaches can be found in U.S. Pat. Nos. 4,445,892 and 4,672,961.
Another approach is to utilize the phenomenon of total internal reflection to redirect the output beam. For example, in U.S. Pat. No. 4,648,890, there is disclosed a probe which has a specially configured tip located beyond the end of the fiber. The tip includes a small chamber filled with air having an index of refraction significantly lower than the material which forms an angled surface at the tip. The laser beam is reflected off the angled surface due to the differences in the indices of refraction of the tip material and the air pocket.
A related approach is described in copending application Ser. No. 07/560,201, filed Jul. 31, 1990, and incorporated herein by reference. This application describes a probe having an integrally formed angled end surface. A sealing member is provided and surrounds the end surface. The sealing member functions to trap air and exclude blood and saline from coming into contact with the angled end surface. Because of the difference in indices of refraction between the fiber and the air within the sealing member, the laser beam is totally internally reflected off the angled end surface and out the side of the fiber.
While the latter approach was effective for redirecting the light energy, it still required an extra sealing member. In addition, the sealing member is subject to failure under the harsh conditions associated with intense laser power.
Accordingly, it is an object of the subject invention to provide a new and improved laser delivery system which overcomes the problems associated with the prior art approaches.
It is a further object of the subject invention to provide a laser delivery system wherein the laser output is redirected out of the side of the optical fiber.
It is another object of the subject invention to provide a probe having only an angled end surface on the optical fiber which can nonetheless redirect laser light out of the side of the fiber.